WASHINGTON — Shifting from the economy to education, Republican presidential candidate Mitt Romneywas proposing a voucher-style system that could significantly alter the public school system and revive the debate over school choice.

Romney, who has been reluctant to stray far from the economic issues at the core of the presidential campaign, was outlining the proposal during a speech Wednesday at the U.S. Chamber of Commerce.

A Romney aide who previewed the speech for reporters said the candidate would let low-income and disabled students use federal funding to attend public schools, public charter schools and, in some cases, private schools. Federal funds could also be applied to tutors or digital courses.

The proposal was not expected to include any new federal money for education.

Romney has so far offered few details for his plans on several key policy areas, including foreign policy, health care and education. He attacked Obama's education policy while speaking to donors in New York City on Tuesday evening, previewing themes likely to play prominently in Wednesday's speech.

"This president receives the lion's share of funding from organized labor, and the teachers' unions represent a massive source of funding for the Democratic Party," Romney said. "The challenge with that is when it comes to actual reform to make schools better for our kids, they talk a good game, but they don't do it."

He continued, "If I'm president of the United States, instead of just giving lip service to improving our schools, I will actually put the kids first and the union behind in giving our kids better teachers, better options and better choices for a better future."

The message is consistent for the Romney campaign, which regularly heaps criticism on the Democratic president's policies but offers only a vague road map for what Romney would do.

White House spokesman Jay Carney said Wednesday that Romney's shift to education was welcome after a campaign season in which he said the GOP rarely mentioned the issue.

"Education never came up in the Republican primary in any of the debates, or if it did, it came up almost never," Carney said.

Carney said Obama's education initiatives have received broad bipartisan support and that the president "looks forward to defending that record."

Romney's shift carries some risk. His regular criticism of labor unions, in particular, threatens to alienate voters in Rust Belt states like Michigan, Ohio and Pennsylvania, where a close election may be decided.

Before the speech, Romney announced Tuesday a team of education policy advisers that includes formerEducation Secretary Rod Paige and other officials from President George W. Bush's administration. Paige is among several prominent opponents of teachers' unions on the panel. As education secretary in 2004, he labeled the National Education Association a "terrorist organization."

Romney's positions on education have evolved over time. He once supported abolishing the EducationDepartment but reversed that position as a presidential candidate in 2007. At the time, he said he came to see the value of the federal government in "holding down the interests of the teachers' unions" and putting kids and parents first.

Romney also changed his position on the Bush-era education overhaul known as "No Child Left Behind." He said he supported the law as a candidate in 2007, but he has since generally come out against the policy many conservatives see as an expansion of the federal government.

Romney continues to support the federal accountability standards in the law, however. He also has said the student testing, charter-school incentives and teacher evaluation standards in Obama's "Race to the Top" competition "make sense," although the federal government should have less control over education. The campaign in recent days has emphasized his support for charter schools while governor of Massachusetts, a theme likely to play out in Wednesday's address.

The speech represents Romney's first public event in four days. Working to close Obama's cash advantage, he's coming off a three-day fundraising swing in the New York area that his chief finance aide said had netted $15 million. A single finance event in Manhattan on Tuesday evening generated $5 million.

Still, the campaign is eager to drive a positive message for voters now tuning in to the contest.

The education speech follows a relatively quiet phase for Romney, who has been focused on fundraising but usually delivers one major address a week. Most of his recent speeches, however, have been about the economic themes that so far have defined his campaign.